Ink jet recording apparatus

Abstract: An ink jet recording apparatus comprises a carriage (2) movable in a given direction with a recording head (1) which is detachably mountable on it and provided with discharge ports for discharging liquid. The apparatus is arranged to include a sensor (21) for detecting the presence or absence of the carriage, the recording head, and at least one of the ink containers. This sensor is provided for the main body of the apparatus and positioned within the movable range of the carriage. With this arrangement, it is possible to simplify the structure required for detecting whether or not these vital elements for recording are installed without any auxiliary power-supply or memory means.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an ink jet recording apparatus for recording characters and images by discharging fine ink droplets onto a sheet, an OHP sheet, a cloth, or other recording medium. Particularly, the invention relates to an ink jet recording apparatus in which at least either one of a recording head and an ink tank is detachably installed on a carriage. Related Background Art There has been known an ink jet recording apparatus for recording by discharging fine ink droplets. This apparatus is advantageous over the apparatuses of other types because of its higher recording speed, easier recording in color, capability of recording not only on a regular sheet, but also on a cloth or other media, a lesser noise, and a higher quality among other features. In general, the recording head of an ink jet recording apparatus has ink discharging ports of one to approximately 200 or 1,000 to approximately 2,000 in order to record on the entire recordable area, while allowing the head to scan a recording medium correlatively. The main scan is such that the carriage on which the recording head is mounted reciprocates to scan for the correlative movement. The subscan is such that a recording medium is scanned in one way in relation to the recording head. Here, the recording head mounted on the carriage is arranged detachably from the carriage or an ink tank which contains ink to be supplied to the recording head is arranged detachably from the recording head. In the former arrangement, the recording head is replaced with a normal one for use if any malfunction takes place in the head or replaced with a new one completely when ink is finished in case of a recording head being arranged integrally with an ink tank. In the latter arrangement, only the ink tank can be replaced with a new ink tank for use while the recording head remains unchanged when ink is finished. However, since the head or the ink tank or both are detachably mounted on the carriage, whether or not the recording head or the ink tank is installed correctly must be examined manually by the user or automatically by the apparatus itself for confirmation when executing a recording operation. An examination of the kind by a user tends to be incomplete, while the automatic examination by a recording apparatus requires a sensor on the carriage. The sensor should be capable of transducing each event of the installation of a recording head or an ink tank into electrical signals, and transmitting them to the main body of the recording apparatus through flexible cables in order to make the required confirmation, and determine whether or not the installation is correctly carried out. However, according to the above-mentioned conventional technique, there is a need for a considerable size of space for the arrangement of the flexible cables, which tends to make the size of the apparatus larger inevitably. Also, the use of durable cables results in a higher cost. Therefore, it is advisable to avoid any provision of flexible cables for the transmission of the electrical signals or it is advisable to minimize the number of cables for this transmission. Also, if a sensor must be mounted on the carriage, the weight of the movable unit becomes heavier that much, necessitating the power of the motor for driving the carriage to be increased accordingly. Further, it take a longer time for the carriage to arrive at a constant speed. As a result, not only the recording speed is reduced, but also, a problem is encountered in that the apparatus should be made larger to the extent that the traveling distance of the carriage is made longer. Also, among such ink jet recording apparatuses, there has been known an apparatus which is arranged to detachably install an ink cartridge in the main body of the apparatus or on a carriage as a source of ink supply so that the provision of ink can be made easily along with the consumption of ink for recording. An ink cartridge of the kind is replaced manually by the operator for use. Further, there has been known an apparatus which is arranged to provide a function to prompt the operator to replace ink cartridges by detecting the remaining ink when such an ink cartridge as above is used. However, in the above-mentioned ink cartridge, it is technically difficult to detect the remaining ink exactly. Also, it costs extremely high if such a detection should be adopted. With a view to solving the problem, therefore, a method is proposed for detecting the ink remains in such a manner that the number of ink discharges from the head is counted, and the counted number is stored in a memory arranged in the main body of the apparatus, thus giving a warning when the stored number reaches a predetermined number of ink discharges. To effectuate this method, it is also necessary to reset the counter arranged for storing the counted number of ink discharges in the main body of the apparatus each time the ink cartridge is replaced. In this case, a switch and a detector for detecting the attachment and detachment of an ink cartridge must be provided. If the required resetting should be carried out by switching, it results not only in an additional cost, but also, in the operations imposed up the operator to execute such as depressing a start key and a reset key in addition to the replacement of the ink cartridges itself. This requires a considerable amount of work on the part of the operator. Also, the cost is inevitably increased by the additional provision of the detector. Moreover, the flow of ink in the ink jet head or in the ink supply pipe should be interrupted when the ink cartridges are replaced. It is then necessary to exercise an extra suction from the ink discharge surface in order to fill ink in the ink passages up to the ink discharge ports. As described above, there is a need for resetting the counter as well as exercising the extra suction when ink cartridges are replaced in a conventional ink jet recording apparatus. Also, it is necessary to detect whether or not the ink cartridge is installed correctly before these extra operations are performed. Here, in a thermal transfer serial printer, it has been known traditionally that a structure is arranged for detecting the position of a carriage, the information regarding an ink ribbon cassette, and the end of the ink ribbon in it by use of an optical sensor provided in the home position for detecting a discriminating portion given to the carriage, a discriminating portion given to the ink ribbon cassette, and a window arranged for detecting the end of the ink ribbon (as disclosed in Japanese Patent Laid-Open Application No. 62-60680, for example). In the thermal transfer printers, there is no possibility that the thermal head is damaged even if no ink ribbon cassette is mounted on the carriage or a printing is erroneously carried out in a state where the ink ribbon in the ink ribbon cassette is used up. In an ink jet recording apparatus, however, there are some cases where the recording head itself should be replaced if the recording head is driven without mounting an ink cartridge or with an ink cartridge but having no ink in it (or with an ink tank which is formed with a recording head to provide an integrated unit, but having no ink in it), because the air and bubbles are mixed in the fine ink discharge ports or ink passages, thus inviting the disabled discharge of ink from the recording head. Also, in a recording head which discharges ink by use of thermal energy, the heater units may be damaged due to excessive heat in such cases. Therefore, in an ink jet recording apparatus, a technique required for detecting the presence or absence of an ink cartridge on a carriage or of the remaining ink in the cartridge is vital to the life of the recording head. Particularly, in consideration of the current technical tendency which results in more frequent replacements of ink containers because of the prolonged life of the head itself, necessitating the replacement of the ink containers more often or in the adoption of a smaller ink container along the miniaturization of the apparatus itself, which also necessitates the replacement of the ink containers more often, the above-mentioned detection technique becomes increasingly more important in recent years. Techniques for detecting the amount of a liquid remaining in a liquid tank are known from the following prior art documents: The English abstract of JP-A-63-2527487 discloses an ink tank for use in an ink jet recording apparatus comprising a member which floats on the ink and has a light reflection portion for reflecting an infrared beam emitted from outside of the ink tank. Document EP-A-0486309 discloses an ink tank comprising a plurality of ink storage chambers and a plurality of movable walls. Each movable wall can move according to a change of amount of ink in each ink storage chamber. Since the movement of the movable walls can be observed externally by using a transparent ink tank case, means for detecting the remaining amount of ink are obtainable. Document FR-A-2492974 discloses an optical liquid level sensor comprising a light reflection prism floating on a liquid. The prism reflects a light beam emitted from a light emitting element to a photodetecting element for detecting the light intensity of the light beam. The detected light intensity is inversely proportional to the distance of the prism to the light emitting and photodetecting elements. The English abstract of JP-A-60-172546 discloses an ink container comprising a transparent ink storage bag having a reflecting member on the top surface side for reflecting a light emitted from outside of the ink storage bag. The relative light intensity of the reflected light changes sharply immediately before the ink runs out. Further, the document EP-A-0573274 discloses an ink tank having an optical passage board provided at its tank wall and cooperating with a light emitting element and a light receiving element for detecting the presence or absence of ink in the ink tank. The optical passage board has an angled part formed by inclined portions which are formed so that the outer surface is at right angles to an incident light emitted from the light emitting element and an exit light totally reflected at an inner surface of the optical passage board and received by the light receiving element. Instead of the angled part, the optical passage board can also be formed to provide a serrated cross section which contributes to implementing a smaller device. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink tank for an ink jet recording apparatus and an ink jet recording apparatus comprising the ink tank which make it possible to easily detect the presence or absence of the ink tank or the presence or absence of ink in the ink tank. The above object is achieved by an ink tank according to claim 1 and an ink jet recording apparatus according to claim 6. The dependent claims set forth developments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically illustrating an embodiment of a recording head having a structure which dually functions to detect the presence or absence of ink. Fig. 2 is a view schematically illustrating a structural example of detecting a specific position of liquid level in an ink cartridge. Fig. 3 illustrates an example of an electrical signal detected according to the structural example shown in Fig. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the accompanying drawings, a detailed description will be made of the embodiments according to the present invention. Fig. 1 is a cross-sectional view showing an ink cartridge 320. The present embodiment shown in Fig. 1 does not need any float. A detection sensor 321 for the remaining ink comprises a light emitting element 321a which emits infrared light 310 and a photodetecting element 321b capable of receiving light from the light emitting element 321a. An light reflection prism 321c is formed integrally with the ink cartridge 320 by polypropylene or some other almost transparent material. Thus, when there is no ink on the inclined surfaces of the head portion of the light reflection prism 321c, the beam from the light emitting element 321a is reflected and caused to arrive at the photodetecting element 321b. On the other hand, when the ink is filled around the inclined surfaces of the head of the light reflection prism 321c, the reflection of the beam from the light emitting element 321a is reduced. The luminous energy which can arrive at the photodetecting element 321b becomes small to make it possible to detect the presence or absence of ink. In this respect, a reference numeral 336 designates an ink supply outlet for supplying ink from the ink cartridge 320 to an ink jet recording head (not shown). Hereinafter, the principle of the detection will be described. The light reflection prism 321c has an angled part formed by inclined portions 341 and 342 almost at 90°. This angled part is arranged in the ink cartridge 320 in such a manner that the infrared light emitted from the light emitting element 321a is reflected by the inclined portion 341, and then, reflected again by the inclined portion 342 to return it to the photodetecting element 321b. Also, at least the part of the inclined portions 341 and 342 where the remaining ink is detected (the position P in Fig. 1, for example) is formed by a material having a light transparency of the same refractive index as or an index extremely close to that of the liquid which is contained in the cartridge or either one side of the inclines portions 341 and 342 is treated by a mirror processing or the like so that the infrared light can be reflected. The specific principle of detection of the remaining ink will be described as follows: The refractive index of the air is approximately 1.0; that of ink, approximately 1.4; and that of polypropylene, approximately 1.5. This is an exemplified material for the formation of the part of the inclined portion 341 or 342 of the light reflection prism 321c where the remaining ink is detected. Here, (1) when ink is present in the ink cartridge 320, the reflective index of ink and that of the material of the part in the detecting position of the remaining ink is extremely close to each other. Thus the infrared light 310 does not reflect on the inclined portion, and (2) if no ink is present in the ink cartridge 320, the reflective index of the air and that of the material of the part in the detecting position of remaining ink is different. Thus the infrared light 310 reflects on the inclined portion. Then, the difference in the luminous energies arriving at the photodetecting element 321b at that time is transformed into electric signals by the known method of photoelectric transformation. In this way, it is possible to detect the presence or absence of ink in the ink cartridge 320. Here, as shown in Fig. 2, a plurality of ink cartridges are mounted on the carriage 351 movably together with the recording head 350. At the same time, each angled part formed by the inclined portions 321 and 322 is positioned upward in the ink cartridge, respectively. The inclined portions are formed by a material whose reflective index is extremely close to that of ink as described above. In this way, it is possible to detect the specific position of the liquid level of ink in each of the ink cartridges. Fig. 3 illustrates an example of electrical signal detected when the carriage on which a recording head and a plurality of ink cartridges are mounted together is moved against a detector 321. The carriage moves against the detector at a constant speed. When the tank Y for yellow ink passes, the detected signal Vout is at a low level Ov only for a time TV. Since this signal is detected in synchronism with the movement of the carriage, it is possible to recognize that it is a signal for the tank for yellow ink. Then, a TM is detected for the magenta tank M. Similarly, thereafter, a TC for the cyan, and a TBk for the black are detected. The low level time for the detected signal has a length which corresponds to the remaining ink. In this way, not only the presence or absence of ink in each of the ink tanks can be detected, but also, the remaining ink can even be detected. In this respect, the detection mechanism described in conjunction with Fig. 18 to Fig. 26 is capable of detecting the remaining ink in the ink tank of such a structure where a recording head and an ink tank are formed together, in addition to being capable of detecting the remaining ink in an ink cartridge. Further, it is possible for such a mechanism to detect the presence or absence of a recording head as well as a reading head arranged on a carriage. Also, there is no longer needed any flexible cable by providing the main body of a recording apparatus with a sensor which is capable of detecting at least one of the carriage and recording head. At the same time, the presence and absence of the recording head and the ink tank can be detected. As a result, a small motor can be employed for driving the carriage, thus making it possible to provide a small ink jet recording apparatus. Furthermore, it is possible to detect whether or not the carriage is in a normal operation at the same time. In this respect, the present invention produces an excellent effect on the recording head or the recording apparatus which is provided with means (such as electrothermal transducers, laser beam, or the like) for generating the thermal energy to be utilized as the energy, thereby the change of state of ink is created to discharge ink for recording, because with this method, it is possible to achieve a highly densified and precise recording. Regarding the typical structure and operational principle of such a method, it is preferable to adopt those which can be implemented using the fundamental principle disclosed in the specifications of U.S. Patent Nos. 4,723,129 and 4,740,796. This method is applicable to the so-called on-demand type recording system as well as to a continuous type recording system. Particularly, it is suitable for the on-demand type because the principle is such that at least one driving signal, which provides a rapid temperature rise beyond a departure from nucleation boiling point in response to recording information, is applied to an electrothermal transducer disposed on a liquid (ink) retaining sheet or liquid passage whereby to cause the electrothermal transducer to generate thermal energy to produce film boiling on the thermoactive portion of the recording head; thus effectively leading to the resultant one to one formation of a bubble in the recording liquid (ink) for each of the driving signals. By the development and contraction of the bubble, the liquid (ink) is discharged through a discharging port to produce at least one droplet. The driving signal is preferably in the form of pulses because the development and contraction of the bubbles can be effectuated instantaneously, thus discharging the liquid (ink) with particularly quick responses. The driving signal in the form of pulses is preferably such as disclosed in the specifications of U.S. Patent Nos. 4,463,359 and 4,345,262. In this respect, it is possible to execute an excellent recording in a better condition if the rate of the temperature increase of the heating surface is adopted as disclosed in the specification of U.S. Patent No. 4,313,124. The structure of the recording head may be as shown in each of the above-mentioned specifications wherein the structure is arranged to combine such discharge ports, liquid passages, and electrothermal transducers as disclosed in the specification (linear type liquid passage or right angle liquid passage). Here, there is also included in the present invention, a structure such as disclosed in the specifications of U.S. Patent Nos. 4,558,333 and 4,459,600 wherein the portions thermally activated are arranged in a curved area. In addition, the present invention is effectively applicable to the structure disclosed in Japanese Laid-Open Application No. 59-123670 wherein a common slit is used as the discharging ports for plural electrothermal transducers, and to the structure disclosed in Japanese Patent Laid-Open Application No. 59-138461 wherein an aperture for absorbing pressure wave of the thermal energy is formed corresponding to the discharging ports. In other words, according to the present invention, recording can be executed reliably and efficiently irrespective of the modes of the recording head. Moreover, as a recording head for which the present invention is effectively utilized, there is a full-line type recording head having a length corresponding to the maximum width of a medium which can be recorded by a recording apparatus. This full-line type head may be the one structured by combining a plurality of the recording heads disclosed in the above-mentioned specifications or a single full-line recording head which is integrally formed. In addition, the present invention is effectively applicable to a replaceable chip type recording head which is electrically connected with the main body of the apparatus, and to which the ink is supplied when it is mounted in the main assembly; or to a cartridge type recording head having an ink tank integrally provided for the head itself. Also, it is preferable to provide additionally means for recovering the recording head, and preliminarily auxiliary means as constituents of the recording apparatus according to the present invention because these additional means will contribute to making the effectiveness of the present invention more stabilized. To name them specifically, such constituents are capping means for the recording head, cleaning means, compression or suction means, preliminary heating means such as electrothermal transducers or heating elements other than such transducers or the combination of those types of elements, and the preliminary discharge mode which is adopted aside from the regular discharging for recording. Also, regarding the kinds or numbers of the installed recording heads, it may be possible to adopt a recording head having only one head for a single color besides those having a plurality of heads for plural kinds of ink having different colors and concentrations. In other words, as the recording mode of the apparatus, for example, the present invention is extremely effective in applying it not only to a recording mode in which only main color such as black or the like is used, but also to an apparatus having at least one of a multi-color mode with ink of different colors, or a full-color mode using the mixture of the colors, irrespective of whether the recording heads are integrally structured or it is structured by a combination of plural recording heads. Furthermore, in the embodiments according to the present invention set forth above, while the ink has been described as liquid, it may be an ink material which is solidified below the room temperature but liquefied at the room temperature. Since the ink is controlled within the temperature not lower than 30°C and not higher than 70°C in order to stabilize its viscosity for the provision of the stable discharge in general, the ink may be such that it can be liquefied when the applicable recording signals are given. In addition, while positively preventing the temperature rise due to the thermal energy by the use of such energy as an energy consumed for changing states of ink from solid to liquid, or using the ink which will be solidified when left intact for the purpose of preventing the ink from being evaporated, it may be possible to adopt for the present invention the use of an ink having a nature of being liquefied only by the application of thermal energy, such as an ink capable of being discharged as ink liquid by enabling itself to be liquefied anyway when the thermal energy is given in accordance with recording signals, and an ink which will have already begun solidifying itself by the time it reaches a recording medium. In such a case, it may be possible to retain the ink in the form of liquid or solid in the recesses or through holes of a porous sheet such as disclosed in Japanese Patent Laid-Open Application No. 54-56847 or 60-71260 in order to enable the ink to face the electrothermal transducers. For the present invention, the most effective method applicable to the various kinds of ink described above is the method in which the aforesaid film boiling can be implemented. Furthermore, as the mode of the recording apparatus according to the present invention, it may be possible to adopt a copying apparatus combined with a reader in addition to the image output terminal which is integrally or independently provided for a word processor, computer, or other information processing apparatus. Also, it may be possible to adopt among others a mode of a facsimile apparatus having transmission and reception functions.

Claims: An ink tank for use in an ink jet recording apparatus containing ink to be fed from said ink tank, characterized by having a light reflection prism (321c) for detecting the presence or absence of ink in the ink tank, said prism (321c) being disposed on an inner surface of the ink tank where a supply portion (336) for supplying ink is provided and comprising an angled part formed by inclined portions (341, 342) for reflecting light emitted from outside of the ink tank. An ink tank according to claim 1, wherein at least the part of said inclined portions (341, 342) where the ink remains are detected is formed by a material having a light transparency of the same refractive index as or one which is extremely close to that of the ink contained in the ink tank, so as to detect the specific position of the ink level in the ink tank. An ink tank according to claim 2, wherein said material is polypropylene. An ink tank according to any one of claims 1 to 3, wherein said prism (321c) is formed integrally with the ink tank (320). An ink tank according to claim 1, wherein the surface provided with said supply portion is a surface lower in a vertical direction in a state where the ink tank to be used is mounted to the ink jet recording apparatus. An ink jet recording apparatus characterized by holding at least one of an ink tank (320) according to any one of claims 1 to 5 for making a recording by using ink supplied from the ink tank, said ink jet recording apparatus further comprising a detection means (321) having a light emitting portion (321a) for emitting light through said surface of the ink tank where said light reflection prism (321c) is disposed and a light receiving portion (321b) for receiving light reflected by the prism, wherein said light emitting portion is arranged on that side of the ink tank where the light receiving portion is arranged. An ink jet recording apparatus according to claim 6, comprising a scanning means (351) for moving said ink tank (320) in a given direction together with a recording head (350), said recording head (350) and said ink tank (320) being detachably mounted on said scanning means, and said detection means (321) being positioned within the range in which said scanning means moves. An ink jet recording apparatus according to claim 7, wherein the light reflected between the inclined portions (341, 342) of said prism (321c) is reflected in substantially the same direction (A) in which the ink tank (320) is moved by the scanning means (351). An ink jet recording apparatus according to claim 7 or 8, comprising a controller (234) for determining whether or not at least either one of said recording head (350) and said ink tank (320) is installed or not by receiving from said detection means (321) the detected signal which is synchronized with the movement of said scanning means (351). An ink jet recording apparatus according to any one of claims 7 to 9, wherein said recording head (350) is provided with electrothermal transducers for generating thermal energy for discharging ink. An ink jet recording apparatus according to any one of claims 7 to 10, wherein said recording head (350) discharges the ink from discharge ports by utilizing film boiling to be generated in the ink by the thermal energy which is applied by said electrothermal transducers.

Inventors: EBISAWA ISAO, HASHIMOTO KENICHIRO, INUI TOSHIHARU, MORIYAMA JIRO, SUGIYAMA HIROSHI, YAEGASHI HISAO, EBISAWA, ISAO, HASHIMOTO, KENICHIRO, INUI, TOSHIHARU, MORIYAMA, JIRO, SUGIYAMA, HIROSHI, YAEGASHI, HISAO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1994
Main classification: B41J2
IPC codes: B41J2, B41J25